Khan Academy is really popular site for students, parents and teachers. Our students will be doing some work on Khan Academy this year. The site uses video lessons to review concepts, and a problems module to check for learning. Students can earn points, awards, and badges by solving different problems.
I highly recommend looking at Khan Academy. You can have your child add you as a "Coach" on the website, which will allow you to track their progress from your own account. You can even add your child as your Coach, and compete with them!
Students really seem to respond well to this website. Please feel free to work ahead of the class with your child!